Stabilizing apparatus for paper webs in the course of formation

ABSTRACT

A stabilizing apparatus for paper webs, comprising at least a movable element ( 4 ) disposed in correspondence of a paper web ( 2 ); tho movable element ( 4 ) comprises a wedge-like portion ( 5 ) having a lower surface ( 7 ) for intercepting an entrained first fluid thread (F 1 ) in correspondence of a lower face ( 2   a ) of the web ( 2 ) and diverting said first thread (F 1 ) along a direction transverse to the advancement direction (A).

The present invention relates to a stabilizing apparatus for paper webs in the course of formation. In particular, the present invention is suitable for use in plants for the production of tissue paper to maintain the webs stable during their advancement along the production lines.

The plants for the production of tissue paper are provided with a roller, so-called “yankee roller” over which the paper web in the course of formation is wound. The web formed on the yankee roller is subsequently sent onto a transmission roller, so-called “pope roller”, to be fed to a spool for collecting the finished product.

Usually, stabilizing devices are provided between the yankee roller and the transmission roller to avoid the formation of air layers between the paper and the outer surface of the transmission roller. The formation of air layers is due to an air flow carried by the paper web and consisting of fluid threads which develop in correspondence of the same web's faces.

It occurs in fact that in some application, the paper web runs at high speed (up to 2000 meters/min) with consequent production of a substantial air flow. Moreover, also the transmission roller, during its rotation thereof, carries a flow of air around the cylindrical surface thereof.

Such formation of air layers generates a cushion effect between the web and the roller (ballooning effect) and an unstable motion of the paper web, so that the latter cannot be properly transported by the transmission roller.

Stabilizing devices for paper webs are known to be made up of a body generally of wedge shape facing the lower surface of the web, that is, the surface which enters in contact with the transmission roller, and provided with an air-delivering means located upstream of the transmission roller.

In these devices, the delivering means directs a jet of air against the lower surface of the web in order to stabilize the same web by counteracting the fluid thread being carried therealong.

However, the stabilizing devices roughly described above exhibits significant drawbacks.

It must be stressed in the first place that the stabilizing devices utilize a jet of compressed air which tends to break the paper web. In fact, it is to be noted that the paper tissue results very thin and, accordingly, also breakable, especially if it is made to advance at high speeds; consequently, the jet of compressed air may tear the web.

The damage of the the paper web also implies the interruption of the production line, with imaginable drawbacks in economical terms.

A further drawback is given by the structural complexity of the delivering means.

Besides, the compressed air delivered towards the web generates an increase of paper powders usually present in the paper-production lines.

In this context, the specific technical object of the present invention is to propose a stabilizing apparatus for paper webs in the course of formation which does not exhibit the above mentioned drawbacks.

In particular, the object of the present invention is to provide a stabilizing apparatus able to efficiently suppress the formation of air under the web without damaging the same web.

A further object of the present invention is to propose a stabilizing apparatus of simple and cost-effective structure and, capable, at the same time, of eliminating the cellulose powders carried by the web,

The above indicated technical object and specified purposes are substantially obtained by providing a stabilizing apparatus for paper webs in the course of formation which comprises the technical characteristics set forth in one or more of the attached claims.

Further characteristics and advantages of the present invention will be more evident from the indicative, and thus non-limitative, description of one preferred, but non-exclusive, embodiment of a stabilizing apparatus for paper webs in the course of formation, as illustrated in the accompanying drawings, wherein:

FIG. 1 shows schematically a region of the paper-production plant wherein the stabilizing apparatus according to the present invention is applied, in a respective operating condition;

FIG. 2 shows schematically the plant of FIG. 1 with the stabilizing apparatus in a respective inoperative condition.

With reference to the attached figures, numeral 1 indicates on the whole a stabilizing apparatus for paper webs 2 in the course of formation, according to the present invention.

In particular, the apparatus 1 is advantageously applied in plants for the production of tissue paper, that is, paper for disposable products of any kind.

In general, the plants, as partially illustrated in FIG. 1, are made up of a roller for driving out a paper web 2 in the course of formation.

The stabilizing apparatus 1 is housed upstream of the above cited roller 3 so as to eliminate any formation of air between the web 2 and the outer surface 3 a of the same roller 3.

In particular, the stabilizing apparatus 1 comprises a movable element 4 disposed in correspondence of a lower face 2 a of web 2.

More in particular, the element 4 exhibits a wedge-like portion 5 having a substantially laminar conformation and presenting a leading edge 6 facing the web's advancement direction A.

The leading edge 6, having preferably a rounded profile, is disposed in correspondence of the lower face 2 a of web 2 in order to intercept a first fluid thread F1 carried by the web 2.

The wedge-like portion 5 also exhibits a lower surface 7 adjacent to said leading edge 6 in order to intercept the first fluid thread F1 and divert it along a direction transverse to the feeding direction A (FIG. 1).

Advantageously, the lower surface 7 of the wedge-like portion 5 has a wavy development to define an aerodynamic profile able to divert the first fluid thread F1.

The wedge-like portion 5 also has a flat upper surface 8 opposite to the lower surface 7 and exhibiting a first end 8 a associated with the leading edge 6, and a second end 8 a opposite to the first.

Upon the deviation of the first thread F1 a depression is created in correspondence of the lower face 2 a of web 2, so that the flat upper surface 8 can be associated with the lower face 2 a of web 2 following the depression created in correspondence of the same lower face 2 a.

In other words, the web 2 is pushed towards the upper surface 8 by sliding thereon while being driven into motion.

The second end 8 b of the flat upper surface 8 is bent away from the lower face 2 a of web 2 and in proximity (in use) of the external surface 3 a of roller 2, thereby defining a section 9 for the passage of a second fluid thread P2 created by the rotation of roller 3.

The passage section 9 delimites, therefore, an expansion region able to create a further depression in correspondence of a portion of the external surface 3 a of roller 3 in contact with the lower face 2 a of web 2. The movable element 4 comprises a support arm 10 having a substantially elongated shape and exhibiting a first end 10 a associated, at the bottom, with the wedge-like portion 5, and a second end 10 b opposite to the first end 10 a.

The first end 10 a is substantially U-shaped wherein a concave region facing opposite to wedge-like portion 5 is defined.

Advantageously, the first end 10 a of the arm 10 has a raker 11 shaped like a lamina ad abutting against the external surface 3 a of the transmission roller 3. In particular, as illustrated in FIG. 1, in which the apparatus 1 is shown in a respective operating condition, the raker 11 is in contact with the roller 3 to slide onto the external surface and to intercept the second fluid thread F2.

In this way, the second fluid thread F2 is mostly diverted by the raker 11 and made to flow to the concave region of the first end 10 a to be drawn away from the web 2.

The second end 10 b of arm 10 is engaged with a linear actuator 12 able to drive the movable element 4 between an operating position, in which it is moved close to the paper web 2 (FIG. 1), and an inoperative position in which it is moved away from the web 2 (FIG. 2).

In this way, in case of possible service operations, the movable element 4 can be moved away from the web to allow an operator to manually intervening on the same web.

The linear actuator 12 preferably exhibits a pneumatic piston. However, it will be appreciated that the actuator 12 may consist of any mechanical means known in the art for driving the movable element 4.

According to a preferred embodiment illustrated in the accompanying drawings, the apparatus 1 may also be provided with suction means 13 to be moved close to the movable element 4 in correspondence of the lower face 2 a of web 2.

In particular, the moans 13 exhibit a first suction mouth 13 a facing the wedge-like portion 5 in order to aspirate the cited fluid threads F1 and F2 being diverted by the movable element 4.

In this way, the paper powders carried by the web 2 and roller 3 are conveyed, together with the fluid threads, F1 and F2 towards the first suction mouth 13 a.

The suction means 13 also exhibit a second suction mouth 13 b facing a yankee roller (not shown in the figures) generally disposed upstream of the movable element 5.

In this way, the web 2 coming from the said yankee roller encounters the leading edge 6 wherein the fluid thread F1 is diverted as above described. As a consequence, the web 2 keeps running in the direction A with the respective lower face 2 a being into abutment against the upper surface 8. In addition, owing to the presence of the arm 10, also the second fluid thread F2 is diverted, thereby eliminating the air between the web 2 and roller 3.

The invention overcomes the problems of the prior art and reaches the envisaged objects.

First of all it is to be stressed, as previously indicated, that the web 2 is stabilized and disposed on the roller 3 without interposition of air. Accordingly, the above mentioned ballooning effect is suppressed.

Besides, the wedge-like portion 5 allows eliminating the fluid thread carried by the web 2 without acting directly on the same web 2. Consequently, any damaging of the paper web 2 is avoided.

Moreover, the structure of the wedgte-like portion 5, made up of a suitably shaped lamina, results of very simple construction and limited cost.

A further advantage is provided by the effect of the means 13 which make it possible to eliminate any cellulose powder present in the plant by aspiring the first and second fluid threads F1 and F2. 

1. Stabilizing apparatus for paper webs, comprising at least a movable element (4) disposed in correspondence of a paper web (2), characterized in that the said movable element (4) comprises a wedge-like portion (5) having a continuous upper surface (8) of contact with a lower face (2 a) of web (2), and a lower surface (7) associated therewith for intercepting a first fluid thread (F1) carried by said lower face (2 a) and diverting said first thread (F1) along a direction transverse to the feeding direction (A) of the web.
 2. Apparatus according to claim 1, characterized in that the said lower surface (7) of the wedge-like portion (5) exhibits an aerodynamic profile to divert said first fluid thread (F1) and create a depression in correspondence of the lower face (2 a) of web (2).
 3. Apparatus according to preceding claim 2, characterized in that the said aerodynamic profile has a substantially wavy pattern.
 4. Apparatus according to claim 1, characterized in that the said wedge-like portion (5) has also a flat upper surface (8) opposite to said lower surface (7), and a leading edge (6) disposed between said upper surface (8) and said lower surface (7); said lower surface (7), upper surface (8) and leading edge (6), all defining a continuous surface.
 5. Apparatus according to claim 4, characterized in that the said flat upper surface (8) can be associated with the lower face (2 a) of web (2).
 6. Apparatus according to claim 5, characterized in that the said flat upper surface (8) has a first end (8 a) associated with said leading edge (6), and a second end (8 b) opposite to the first (8 a) and bent away from the lower face (2 a) of web (2); said second end (8 b) defining, in cooperation with an outer surface (3 a) of the transmission roller (3), a section (9) for the passage of a second fluid thread (F2) carried by the same roller (3).
 7. Apparatus according to claim 6, characterized in that the said passage section (9) forms a neck for determining the expansion of the second fluid thread (F2) and create a depression in correspondence of a portion of the external surface (3 a) of roller (3) in contact with the lower face (2 a) of web (2).
 8. Apparatus according to claim 6, characterized in that the said movable element (4) comprises also a support arm (10) having a first end (10 a) associated with said wedge-like portion (5), and a second end (10 b) opposite to the first (10 a); said first end (10 a) exhibiting a substantially unshaped development which defines a concave region.
 9. Apparatus according to claim 8, characterized in that the said first end 10 a) of the support arm (10) exhibits an extension (11) shaped like a lamina and abutted against the external surface (3 a) of the transmission roller (3) in order to divert the second fluid thread (F2) towards the second end (10 b) of said arm (10)
 10. Apparatus according to claim 8, characterized in that it comprises also a linear actuator (12) associated with the second end (10 b) of said arm (10) in order to drive the movable element (4) between an operating position in which it is moved close to the paper web (2), and an inoperative position in which it is moved away from said web (2).
 11. Apparatus according to claim 1, characterized in that it comprises also suction means (13) moved close to said movable element (4) and disposed in correspondence of the lower face (2 a) of said web (2).
 12. Apparatus according to claim 11, characterized in that the said suction means (13) comprise a first mouth (13 a) facing said wedge-like portion (5) to aspirate said first fluid thread (F1) diverted by the lower surface (7), and a second suction mouth (13 b) facing a yankee roller disposed upstream of said movable element (4).
 13. Suction box (13) for tissue paper-production plants which include a smooth cylinder and a pope roller, the box comprising a first suction mouth (13 a) facing said pope roller, and a second suction mouth (i3 b) facing said smooth roller. 